Dashpot for machine tools



Oct. 4, 1960 A. v. KLANCNIK 2,954,851

. DASHPOT FOR MACHINE TOOLS Filed Aug. 25. 195B 2 Sheets-Sheet 1 VALVE SPOOL XLO IN V EN TOR. BDOLPH V KLANCNIK Eil/5- Oct. 4, `1960 A. v. KLANcNlK nAsHPoT Foa MACHINE TooLs 2 Sheets-sheet 2 Filed Aug. 25. 1958 JNVENToR. ADOLPH KLANCNM DAsHPoT FOR MACHINE Tools Adolph V. lancnk, Glenview, Ill. Filed Aug. 2s, 195s, ser'. No. 756,941

1 Claim. (Cl. 18s-9v) This invention relates to a control for automatic machine tools wherein a tool is mounted for reciprocating automatically controlled strokes toward and away from a work piece incidental to tapping, broach-in-g, reaming or like operations performed on the work piece.

One of the more common forms of machine tools is one wherein a drill or like rapidly rotating tool is mounted for rotation at the end of a piston which is mounted in a cylinder for forward and reverse strokes relative to the work piece being operated upon by the tool. Thus, when the work piece is to be subjected to the function of the tool the chuck in which -the tool is gripped is set in rotary motion, and the piston which carries the chuck is subjected to its forward stroke causing the tool to engage the work piece. It may be that an opening or recess is being drilled, an opening is being counter-sunk, an end is being rounded oit or chamfered, and so on, and in many of these operations it is desirable that there be a slight dwell of the rotating tool at the bottom of its stroke, say. for ten revolutions or so, either to account for accurate depth control over a drilled opening or nal smooth-ing of 'the surfaces that were operated on by the tool. One of the primary objects of the present invention is to enable such dwell of the rotating tool to be controlled in a relatively simple, inexpensive and eilicient manner, and to be able to establish a great deal of accuracy in lthe amount of dwell.

It is also common ,practice in this art to associate a dash pot with the piston which carries the rotating tool for various diiferent purposes, but for the most part such dash pot control Iaccounts for increasing resistance to the forward stroke of the piston just prior to and during the time that the drill or other tool is engaging the work piece while performing the essential machining operation. For example, it is common to utilize dash pot resistance at a time just prior to the drill breaking through the far side of the work piece, and also to exert dfash pot resistance on the drill at the moment it engages the work piece. Moreover, it is advantageous to cut out the dash pot or at least to account for a release of its resistance during the time that the piston is on its reverse or back stroke, since this greatly speeds up operation of the machine. Another object of the present invention is to construct a relatively simple and inexpensive dash pot for use in machine tools, and to associate with this dash pot the depth control or ldwell control device referredto rates latent the present invention 'and the purview of the appended claim.

In the drawings:

Fig. 1 is a schematic View of a reciprocatory machine Fig. 5 is a sectional view of the assembly illustrated` in Fig. 3 taken on section lines 5-5 of Fig. 3; and

Fig. 6 is a detailed sectional view of a switch actuating mechanism utilized in the present invention and taken substantially on the section lines 6--6 of Fig. 3.

With particular reference Inow to the drawings and in the rst instance to Fig. l, there is generally designated at 1 a reciprocating machine tool which may be a drill,'

reamer, broaching tool or the like. The cutting tool 2 thereof is adapted to be advanced toward and away from a work piece 3 by means of a so-called platen 4 having a spindle 5 rotatably mounted therein. Any suitable power means, not shown, may be provided to rotate the tool-carrying spindle. Tools of this type are custom- Y arily provided with some power means for advancing the tool toward the work piece and retracting it therefrom and in the embodiment of the invention illustrated in the drawings this means is shown as a Ipair of iluid cylinders 6 having the pistons thereof connected to the platen 4.,v Fluid, which may be` air, is selectively admitted to onev end or the other of the cylinder means 6 under contro-l of a suitable Z#way valve 7. The valve may utilize .a iirst solenoid 8 for shifting the valve spool to one limit to admit -iluid to the upper ends of the cylinders illustrated, thereby causing advance movement of the tool.

A second solenoid 9 may, when energized, shift the valve is now considered to be the best mode contemplated for spool in the opposite direction so' as to admit duid to the other end of the cylinders 6 for causing retracting movement of the tool 2.

Machine tools of this character usually include an auto- Y `matic work holding mechanism in the form of relatively movable jaws diagrammatically represented at 3a and 3'b.

A -ui-d cylinder 3c is adapted to move one jaw 3a toward the other to grip -the work piece therebetween. A switch Patented oat. 4, 1960,

3d, Fig. 2, is in the circuit to the advancing solenoidl 8 and is closed when the work piece is firmly held by the jaws, thus conditioning the advancing solenoid circuit for operation. manual on-and-oi switch (not shown) in the circuit t0 the solenoids and tool reversing switches 11 and 12,

which as shown in Fig. 2 are in circuit with the solenoids 8 and 9, respectively. One switch 12 may be actuated Systems of this character may also include a when the tool reaches a predetermined poi-nt in its travel as, for example, that point in the movementof the tool corresponding to the maximum penetration of the tool in the work piece. The switch 12 is closed, at that time,

thus energizing the solenoid 9 to shift the valve and cause return movement of the tool. other hand, will only be closed for energizing the solenoid 8 when the tool is at the opposite or retracted position' f of movement, thus automatically reversing the tool. A

The switch 11, on theV v switch actuating mechanism, diagrammatically reprey:

sented at 13 in Fig. 1 is interconnected with the tool carrywhile at the end of the retracting stroke switch llfis closed while switch 12 is opened.` Machine tool systems of this character are designed for automatic, conti,nuollily,-,

reciprocating operation.

These hole forming tools are usually provided 1 some form of dash pot control device whichretards" movement od the tool at some preselected stage of operation Ynear the end of its work performing stroke so as to avoid a breakthrough. In accordancey with the invention, a dash pot v14 is mounted on the main cylinder block of the machine tool.' The dash pot includes cylinder 15 formed therein, and a plungerl-G having ay piston head 16Pv adapted for lreciprocal axial movement in the cylinder 15. The dash' pot includes a reservoir 17, the axis of which is parallel to the7 axis of the cylinder 15 and which contains a suitable hydraulic Huid.

Both the cylinder space and -reservoir space in the dash pot may b' cast with the block or they may be formed from drilling. A plug 17a closes one end of the f reservoir.

A needle valve 18 is adapted for adjustably restricting flow of fluid from one end of \the dasl1 pot cylinder through ya passage 19 so thatduring movement of the plunger 1 '6 to the left, as illustrated in Fig. 5, fluid will be `forced from the cylinder 15 through the restricted passage 19 and into the reservoir. Thus, the restriction for the escape of the fluid retards movement of thexplunger toward' the left. The other or right-hand end of the cylinder 15 communicates through a drain passage 20 with the reservoir so tha-t upon movement of the plunger tothe right fluid is forced through the passage 20 without restriction and into the reservoir. The drainport maybe drilled through the wall between the cylinder and reservoir at the same time that an aligned lling opening 20ct is formed.

A spring-biased check valve 21 is provided in ak passage 22 which establishes communication between the reservoir and the needle valve end of the dash pot cylinder, so that upon return movement of the plunger 16 uid readily ows through the passage 22 and'intothe dash pot chamber or cylinder. The check valve prevents opposite flow of uid from the cylinder to the reservoir. A plug 22a closes thebore leading to the check valve passage, and the needle valve 18 is advantageously threadably mounted in a nut plug 23 in turn threadedly mounted in the dash pot housing, so that by turning the head 18b of the needle valve, the point of this valve is moved Itoward and away from the passage 19 so as to vary the size of the restricted opening and thus vary the retarding resistance offered to the ow of hydraulic fluid from-the dash pot`chamb`er.l

The plunger 16 is supported for sliding movement in a bearing 16b`in the dash pot and extends outwardly from the dash pot housing. The end of the plunger opposite the piston part 16p is threaded as at 22T and carries adjustable stops 23S inI threaded engagement with the portion 22T. In order to cause movement of the plunger within the cylinder and-toward the'left and thus retard movement of the tool during its advancing stroke, a spider 24 (see Fig. 1) may be xed to the tool carrying platen. An arm "25 is fixed to the spider 24 and includes' an off-set portion 26, Fig. 3, at one end thereof which is adapted for abutting engagement with the stops 23S at a-predetermined point of the movement of the tool; As the ltool advances in'its work performing o pzration,v

the arm 25 may move'tothe left as seen in Fig.l 3 andy engage the'stops 23S near the end of its'worlc performing-f strokeand If orce'th'e piston 16p to the left in the cylinder 15.'r Thus the plunger and dashpot retard the' rial movement of the tool. By threadably Iadjusting the position ofthe stop's`23S on the plunger, the point'in the travel of the tool'at which the dash pot is actuated may be selectivelyy varied in accordance with the desired length Y of the-work performing stroke of thetool and in accord"- ance'with the amount of movementdesired tobe retai'ded. y

The' off-'set' portion 26 of tliearm 25' has a bore 27 through whichthe'outer end of the plunger 116 is ref ceived. The plunger preferably ycarries a 'washer 28 at, its extreme outer rend which isl adapted Vto "sea-tj in a re,-`

l d cess 29 in the end of the off-s etportionz. Thus, after the arm 25 has moved to the left during the work performing stroke of the tool and caused inward movement of thedash pot plunger and then moves to the right during the retracting stroke of the tool `the surface of the recess 29 will engage the washer 28 and force the plunger of the dash pot to the right, thus setting up the plunger for the next work performing stroke of the tool.

Pressure V responsive means are# proyiided for de-energizing the circuit controlling the solenoid 49 which during energize-tion thereof actuates the valve 7 to cause retracting movement-.gf the .togl- Thus @normally closed micro switch 30 is mountedon one sident the dash pot housing and includes an actuating member 31 which when depressed opens the switch. The switch 30 is in the wiring leading to the solenoid 9. When the switch 30 is open, the circuit to the solenoid controlling the retracting movement ofthe tool is deactivated. v Y

Means lare provided for opening the switch 30 and holding it open for a period of time corresponding to the desired period of dwell time of the tool in the work piece. Tov this end, anauxiliary cylinder 32 is mounted on the dash pot housing fand includes a piston 33 therein, Fig. 6, having arod34 extending outwardly from the cylinder and positioned4 for contact with theactuating member 31 of the switch 30 so that during movement of -the piston as to the right in Fig. `6, the switch 30 is opened. A pressure equalizing conduit 35, Fig. 3, leads from the dash pot cylinder to the auxiliary cylinder32 and has a passageway 36 therein which admits duid to the auxiliary cylinder 32 at a pressure corresponding to the pressure in the dash pot' cylinder. Fluid from the passage 36 Hows through a passage 37 into the cylinder space in which the piston 33 operates so as to subject the piston 33 to the pressure i`n the das-l1 pot cylinder. A springrbiased check valve 38 interposed-in the passage 37 allows free entry of the uid from the passage 36 into the working area of the cylinder in which piston 33 is disposed, but prevents its return through the passage 37. A lluid return from the working space is provided through a return port 39 communicating at respective ends with passage 36 and the cylinder space and which is restricted by an adjustable needle valve 40. The needle valve 40 is threadably mounted in a bearing support 41 so'that the operator, Iby lturning the handle 42 of the needle valve, may adjust the restricting effect on'the passage 39.V Thus when the dash pot'piungei- 16'is` caused to move inwardly in the dash'pot cyliiider,'as when the tool'nears the end ofits workperforming'l stroke, the

pressure in the das-hipogt cylinder will build up due to the restricting effect of the needle valve 18 and the same pressure will be developed inthe working `areiofwthe cylinder 32' through'the passage 37. This buildupin pressure'for'ces the piston 33'to the right as viewed in Fig. 6 and thusr opens the switch 30 and deactivates the circuit leading to the'` tool retracting solenoid, When the tool reachesits final advanced position within the work, the switch'12'is'-' closed,- `but the circuiti, to the solenoid '9`v is open byre'ason of the opening'of. the switch 30. At thispoint'in the Itravel of the machine tool, the other solenoid S'isalsol de-energized. Fhe'plunger 16 alsostops andthe pressure in the dash pot cylinder quickly diminishes due rto.theliuid'which escapes past the needle valve 18 into the reservoir. The pressure in the auxiliaiy cylinder 32; however, VClirnir`1is'l`1es at a slower rate' due-to the fact that adrop in pressure in the dash pot cylinderwill not'caus'e' o'w ofuid inta return directionpast the check'valve 3 8.` The p'ressure inv the working area olf the cylinder 32 diminishes slowly due to the restricting effect' of the needle valve r40". When the pressure in'thecylinder 32" has diminished'to a predeactuating contact with the switch member 31.- Switch 30 then closes, and since switch 12 is closed at that time, solenoid 9 is then energized and the tool is retracted.

Thus the switch 30 lwill be opened upon a build up of pressure in the dash pot chamber and will be held open for a period of time after movement of the dash pot plunger stops. This period of time may be adjusted by adjusting the needle valve 40 so as to vary the restricting effect in the passage 39. I'hus the tool will dwell at the end of its work performing stroke :for a period of time selected by the operator and adjusted through adjustment of the needle valve 40.

In order to eliminate the circuit opening *function of switch 30 in the event that the operator does not desire use of the pressure responsive dwell switch, the switch 30 may be adjustably mounted on the dash pot housing as by means of bolts 44 and 45 which are received through slots in a mounting plate for the switch and received by the daseh pot housing. Thus the switch actuating member may be adjusted with the switch to a position wherein it will not be contacted by the piston rod 34 of the auxiliary cylinders. In this position the switch remains closed during the operation of the switch and allows complete control of the tool through the other switches of the tool control circuitry.

The retarding and dwell time system of the present invention is extremely compact and simple and may be applied to existing reciprocatory machine tool systems.

It is positive in action and its dependency on the pressure developed by the dash pot cylinder el-iminates the need for complicated dwell time control circuitry which in many instances are quite complex, overly sensitive to malfunctioning, and oppresively expensive. Hence, while I have illustrated and described a preferred embodiment of my invention it is to be understood that this is capable of variation yand modification, and I therefore do not Wish to be limited to the precise details set forth, but desire to avail myself of such changes and alterations as fall within the purview of the following claim.

I claim:

A dash pot for use in retarding movement of a reciprocable tool at a preselected stage of operation of the tool and comprising a housing having two parallel extending cylindrical bores formed therein, one of which bores is adapted to act as a reservoir and the other of which bores forms a cylinder, the section of the housing disposed intermediate the bores having a rst conduit interconnecting adjacent ends of the reservoir bore and cylinder bore, a metering valve threadedly mounted in one wall of the housing and projecting within one end of the first conduit to form a variable area and continuously open metering orifice therewith, said section of the housing having -a second conduit extending parallel and closely adjacent to the first conduit, said second conduit having a rst opening in said reservoir bore and a second open ing communicating with the end of the rst conduit opposite the metering orifice, a ball check valve disposed within the second conduit and spring biased to a position wherein uid flow from said tirst conduit through the second conduit to the reservoir bore is electively prevented but tiuid ow from said reservoir through the second conduit to said first conduit is permitted, said V.section of the housing having a third unrestricted conduit interconnecting the ends of the reservoir bore and the cylinder bore opposite the ends interconnected by the lirst conduit, said housing having a lling passage formed in the wall of 4a housing and aligned with said third conduit, a plunger piston slidably disposed Within the cylinder bore between the iirst and third conduits whereby the rate of movement of said piston inwardly of thebore is regulated by the position of said valve within the orice and movement of said piston outwardly of the bore displaces uid rearwardly of the piston through the third conduit and induces uid from the reservoir through the second conduit and past the spring biased check valve to the piston bore to provide rapid outward movement of the piston, said plunger piston having adjustable stop means for providing a variable lost motion connection with a piston actuating mernlber aixed to the tool to be retarded.

References Cited in the tile of this patent UNITED STATES PATENTS 1,595,171 Shonnard Aug. 10, 1926 2,243,580 Rosch May 27, 19411 2,346,359 Claus Apr. 11, 1944 2,354,889 Smith Aug. 1, 1944 2,367,799 Robinson Ian. 23, 1945 2,580,751 Fletcher Ian. 1, 1952 2,723,007 Lanphere Nov. 8, 1955 2,730,201 Melzer Jan. 10, 1956 2,780,116 Schafer Feb. 5, 1957 FOREIGN PATENTS 590,291 France Mar. 13, 1925 

